12. f3e1 Ding chooses an interesting plan, more or less typical of the English Opening, although it looks a bit funny: to play f2-f4 without moving any of the central pawns. 12... f8e8  13. f2f4  13... e5f4 The sharpest continuation. 14. f1f4 This is the point of White's plan. The rook becomes active, the knight can go to d3, and we have a strange position on the board with White's central pawns still on their initial squares.